Figure 5 |. Metasurface-enabled molecular fingerprint retrieval from complex and spatially heterogeneous biological tissue regions.

a, Murine brain tissue section imaged in transmission mode at 1574 cm⁻¹ wavenumber showing areas both on and off the metasurface, which is enclosed by white dashed lines. The resonant plasmonic metasurface visibly enhances molecular absorbance when compared to tissue regions imaged on a standard substrate (regions outside of the dashed lines). b, c, d, Second derivative absorption spectra acquired in reflection mode from four different brain regions $R_1$, $R_2$, $R_3$, and $R_4$ on the metasurface (solid lines) and reference spectrum (dashed line). Reference spectra (ref) of a brain tissue section with thickness 20 μm, mounted on a gold mirror, was referenced to a front-surface gold mirror. e, f, and g, Substrate band fitting analysis on three plasmonic resonance spectral regions for a brain tissue section on the metasurface confirm that the SE-MIRSI can capture fine spectral signatures from nanoscale surface volumes without the need for bulk tissue light-matter interactions. h, i, and j, Band fitting analysis on three different regions of absorption spectrum from tissue section on a standard MIR substrate.